This invention relates to a machine for making and dispensing semiliquid and/or semisolid food products such as, for example, soft ice cream and the like.
More specifically, this invention relates to machines for making ice cream where the basic product for making the ice cream is contained in a sealed container of soft plastic enclosed in cardboard box and commonly known by the term “Bag in Box”.
Machines of this type for making and dispensing ice cream comprise a frame which mounts, at the top of it, an operating unit for making and dispensing the ice cream.
The operating unit comprises a cooling cylinder, commonly called mixing and freezing unit, inside which the basic product is processed. When the product is ready, it can be served through a dispensing tap which is usually mounted on the front of the machine frame.
These machines also comprise an intake pump which feeds the basic product from the sealed container through an intake pipe into the mixing and freezing cylinder.
More specifically, the pump—usually a mechanical gear pump—takes in a mixture of air and basic product and feeds it into the cylinder at a predetermined, preset pressure.
In order to keep the pressure at which the mixture is fed into the cylinder at the correct level, the prior art teaches the use of a by-pass valve which is located downstream of the gear pump and which, when the pressure of the mixture exceeds the value of the valve rating, opens and bypasses the cylinder by feeding the product for example into a recycling tank.
In another prior art solution for keeping the pressure at which the air and product mixture is fed into the cylinder at the correct level, a pressure sensor is placed on the base plate of the cylinder. This solution, however, is disadvantageous because it gives rise to problems of precision and cleaning and hence sanitization.
This type of problem also applies to gear pumps since these are very difficult to clean and sanitize.
Another disadvantage of these machines is due to the fact that the basic product consists of a highly perishable milk-based mix, which favors the growth of germs and bacteria, especially at the parts which come into direct contact with the basic product.
For example, the end of the intake pipe connected to the sealed container normally has a needle or tip for piercing the container itself. When an empty container is removed and changed for a new one, the needle comes into contact with the air, creating a possible site for bacterial growth, with the risk of contaminating the basic product in the new container.
These machines are therefore subjected to frequent checks and preventive maintenance in order to guarantee perfect hygiene conditions along the entire feed circuit.
These needs are connected directly with the difficulty of disassembling the above mentioned pumps of the prior art type.
Maintenance operations of this type, however, cannot guarantee conditions of total product hygiene.
Although methods for estimating the cell mass of a bacterial population exist, these methods involve laboratory tests, high costs and extended times and are used, for example in the dairy industry, only in random testing.